Aspects of the invention can relate to a projector for projecting images using a light modulation device, such as a liquid crystal panel. As a related art illumination device for a liquid crystal panel incorporated in a projector, there is a device that separates a light source beam from a white light source into three colors and, provided with a relay system in the illumination light path of red of them, compensates differences in optical lengths from remaining green and blue. See, for example, Japanese Patent Application Publications Nos. Hei-10-171045, 2003-287804, and Hei-11-242184. Of these, in one illumination device, the relay system can be formed by four lenses and an adjustment mechanism of a slotted hole and an adjustment screw is provided to one lens at the central side, and thereby, the lens is made vertically and horizontally movable within a vertical surface orthogonal to the light path. See Publication No. Hei-11-242184.
Further, as another illumination device for a liquid crystal panel, there is a device that separates a light source beam from a white light source into three colors and, provided with a relay system in the illumination light path of blue of them, compensates differences in optical lengths from remaining two colors. See, for example, Japanese Patent Application Publication No. Hei-11-64977. In this projector, effective utilization of blue light is intended by making the central lens of three lenses forming the relay system movable in an optical axis direction, for example, for scaling up and down of the size of the illumination area for the liquid crystal panel.
Further, as another related art illumination device for a liquid crystal panel, there is a device that separates a light source beam from a white light source into three colors and, provided with light guiding device, such as a relay system in the illumination light path of green of them, compensates differences in optical lengths from remaining two colors. See, for example, see International Publication No. WO 94/22042.
However, in the illumination device provided with a relay system in the illumination light path of red, because a high-pressure mercury lamp or the like is used as the light source, the red becomes weaker compared to the other colors, and sometimes the white balance can not be suitably adjusted. In such a case, the white balance can be achieved by signal processing of adjusting brightness values of image signals to be input to the liquid crystal panel, however, there can be a problem that the brightness and contrast of the image is reduced.
Further, in the related art illumination device in which the lens provided in the red light path is made vertically and horizontally movable within a vertical surface orthogonal to the light path, the effect is only that the illumination light can be suitably entered into the illumination area of the liquid crystal panel.
Further, in the related art illumination device in which the lens provided in the red light path is made vertically and horizontally movable in the optical axis direction, the loss of blue light, the amount of light of which is apt to be insufficient, can be reduced and the waste of the illumination light can be prevented, however, the bias of the white balance due to the luminescence property of the high-pressure mercury lamp or the like can not be resolved in a positive manner.
Further, in the related art illumination device provided with a relay system in the illumination light path of green, because the white balance often varies largely with respect to each product due to the luminescence property of the high-pressure mercury lamp or the like, signal processing for adjusting brightness values of image signals to be input to the liquid crystal panel larger is required.